FITBODY Exercise Library · Core
Reverse Crunches
Reverse crunches are a controlled core exercise that curl the pelvis toward the ribs, training the rectus abdominis, deep core, and hip-flexor control without pulling on your neck.
What Is a Reverse Crunch?
A reverse crunch is a core exercise where your upper body stays mostly still while your pelvis curls toward your ribs. Instead of lifting your shoulders toward your hips like a standard crunch, you draw your knees in and lift your hips slightly off the floor with control.
You may also hear reverse crunches called knee curl ins, ab knee tucks, or ab tuck ups. The important part is the same: your abs create the curl, not momentum from swinging your legs.
The original Julie Lohre page also demonstrates a weighted variation with a barbell held overhead. That version is more advanced because the barbell adds a stability challenge through the upper body while your core controls the knee tuck. Start with the bodyweight version first. Earn the load. No need to turn abs into a circus act on day one.
How to Do Reverse Crunches
Make this smaller than you think. A tight little pelvic curl will light up your abs far better than a huge leg swing. If your knees are flying toward your face, your momentum is doing the work. Your abs are just along for the ride.
Reverse Crunch vs. Weighted Reverse Crunch with Barbell
The basic reverse crunch keeps your arms on the floor and lets you focus on learning the pelvic curl. That is the version most people should master first, especially if your low back tends to arch during core work.
The barbell reverse crunch adds a light barbell held over the chest or slightly overhead. This can increase the stability demand through the shoulders, lats, rib cage, and trunk. It can also go sideways fast if you choose a bar that is too heavy or let the arms drift.
If you want more core progressions, pair reverse crunches with the hollow body hold for anti-extension strength or the plank for full-body core stability. For a related weighted core movement, use the ab barbell leg curl in only when you can keep your low back controlled.
What Muscles Do Reverse Crunches Work?
Reverse crunches primarily train the rectus abdominis, the long abdominal muscle running down the front of the torso. The movement also uses the obliques and deep core to stabilize the pelvis and spine, while the hip flexors assist with bringing the thighs toward the torso.
You may feel this exercise more in the “lower abs,” but anatomically the rectus abdominis is one continuous muscle. The coaching goal is not to isolate a separate lower-ab muscle; it is to control posterior pelvic tilt and lift the hips without swinging.
See the full muscle breakdown
- Rectus abdominis: Flexes the spine and helps curl the pelvis toward the ribs during the reverse crunch.
- Transverse abdominis: Helps brace the trunk and keep the low back from arching as the legs move.
- Internal and external obliques: Assist with trunk stability and help control the pelvis through the curl.
- Hip flexors: Help bring the thighs toward the torso, especially if the movement becomes more of a knee tuck than a pelvic curl.
- Lats and shoulders: In the barbell version, these help stabilize the weight overhead and keep the rib cage controlled.
- Neck muscles: Should stay relaxed. One advantage of reverse crunches is that your head can remain on the mat instead of being pulled forward by your hands.
Sets and Reps
Reverse crunches work best when the reps are controlled. If you can only feel them when you swing your legs, slow down and shorten the range. Core training is not a leg-flinging contest.
| Goal | Sets | Reps | Rest |
|---|---|---|---|
| Learning the movement | 2-3 | 8-10 slow reps | 45-60 seconds |
| Core strength | 3-4 | 10-15 reps | 45-75 seconds |
| Weighted variation | 2-3 | 6-10 controlled reps | 60-90 seconds |
| Core finisher | 2-3 | 20-30 seconds | 30-45 seconds |
One rep means one controlled hip curl up and one controlled lower back to the starting position. Progress by improving control first, then adding reps, then trying the weighted version if your form stays locked in.
Reverse Crunch Variations and Modifications
Bent-Knee Reverse Crunch
This is the standard version and the best place to start. Keep the knees bent at about 90 degrees and focus on curling the pelvis up instead of kicking the feet.
Reverse Crunch with Feet Tap
Lower your feet toward the floor after each rep and lightly tap down before curling again. This makes the exercise more manageable if holding the legs up the whole time causes your back to arch.
Reverse Crunch with Barbell Overhead
Hold a very light barbell over your chest or slightly overhead while performing the reverse crunch. Keep your arms steady, ribs down, and shoulders packed. This variation should feel like a core stability challenge, not a shoulder survival test.
Weighted Reverse Crunch
Use a light medicine ball, dumbbell, or barbell only after you can control the bodyweight version. Add load gradually and stop if your low back starts arching.
Incline Reverse Crunch
Perform the reverse crunch on a slight incline or hold a stable bench behind your head. This can make the top of the movement more challenging, so keep the reps slow and strict.
Hollow Body Prep
If reverse crunches feel sloppy, build control with a hollow body hold first. Learning to keep the low back pressed down makes almost every ab exercise cleaner.
Common Reverse Crunch Mistakes
- Swinging the legs. Slow down and make the hips lift because the abs curl the pelvis, not because your knees are flying toward your face.
- Letting the low back arch. Keep the ribs down and lower only as far as you can control. If your back pops up, shorten the range.
- Lifting too high. The hip lift should be small. Rolling too far can turn the movement into momentum instead of abdominal control.
- Pushing hard through the arms. Your hands can stabilize you, but they should not be doing the main work.
- Adding weight too soon. A barbell overhead is only useful if your basic reverse crunch is clean. Load does not fix bad form; it just makes bad form louder.
- Holding your breath. Exhale as you curl up, then inhale as you lower with control.
Reverse Crunch FAQs
Are reverse crunches good for lower abs?
Reverse crunches are a good exercise for training the rectus abdominis with an emphasis on pelvic control. Many people feel them more in the lower portion of the abs because the pelvis curls toward the ribs. Just remember that the rectus abdominis is one continuous muscle, so the goal is better core control, not isolating a separate lower-ab muscle.
Do reverse crunches burn belly fat?
Reverse crunches can strengthen and build your abdominal muscles, but they are not a magic belly-fat burner. Fat loss still comes from overall nutrition, calorie balance, strength training, cardio, daily movement, sleep, and consistency. Use reverse crunches to train the abs, not to chase spot reduction.
Why do I feel reverse crunches in my hip flexors?
Some hip-flexor involvement is normal because your thighs are moving toward your torso. If your hip flexors take over completely, slow down, reduce the range, and focus on curling your tailbone up instead of pulling your knees in. The cleaner the pelvic curl, the more the abs do the job.
Are reverse crunches better than regular crunches?
They are not automatically better; they are different. Regular crunches lift the shoulders toward the hips, while reverse crunches curl the hips toward the ribs. Reverse crunches are often a good option for people who dislike neck strain during traditional crunches because the head can stay relaxed on the mat.
Should beginners do weighted reverse crunches?
Most beginners should master bodyweight reverse crunches first. Once you can keep your low back controlled and avoid swinging, you can try a light weighted variation. Start lighter than you think and treat the weight as a stability challenge, not a max-effort lift.
How many reverse crunches should I do?
Start with 2 to 3 sets of 8 to 10 slow reps. As your control improves, work toward 10 to 15 reps per set. Stop the set when your form breaks, because sloppy reverse crunches quickly turn into leg swings.
References
- Escamilla RF, Babb E, DeWitt R, Jew P, Kelleher P, Burnham T, Busch J, D’Anna K, Mowbray R, Imamura RT. “Electromyographic analysis of traditional and nontraditional abdominal exercises: implications for rehabilitation and training.” Physical Therapy, 2006, 86(5):656-671. PMID: 16649890. Supports that reverse-crunch-style movements can produce meaningful abdominal activation; the study tested several variations and noted that high hip-flexor activity may be an issue for some people with low-back problems.
- Willett GM, Hyde JE, Uhrlaub MB, Wendel CL, Karst GM. “Relative activity of abdominal muscles during commonly prescribed strengthening exercises.” Journal of Strength and Conditioning Research, 2001, 15(4):480-485. PMID: 11726260. Supports that reverse-curl style abdominal exercises can strongly activate the lower rectus abdominis region and external obliques; EMG activation does not prove fat loss or hypertrophy outcomes by itself.
- Clark KM, Holt LE, Sinyard J. “Electromyographic comparison of the upper and lower rectus abdominis during abdominal exercises.” Journal of Strength and Conditioning Research, 2003, 17(3):475-483. PMID: 12930172. Supports a more cautious interpretation of upper-versus-lower rectus abdominis activation, since reverse curl-up was not superior to every trunk-curl variation in that study.
- American College of Sports Medicine. “Progression Models in Resistance Training for Healthy Adults.” Medicine & Science in Sports & Exercise, 2009, 41(3):687-708. DOI: 10.1249/MSS.0b013e3181915670. Supports progressing resistance training by adjusting load, repetitions, volume, and training status; it does not prescribe weighted reverse crunches specifically.
- Brobakken MF, Krogsaeter I, Helgerud J, Wang E, Hoff J. “Abdominal aerobic endurance exercise reveals spot reduction exists: A randomized controlled trial.” Physiological Reports, 2023, 11(22):e15853. PMID: 38010201. This study reported local trunk-fat changes in overweight adult men using a specific abdominal endurance protocol, but it did not test reverse crunches alone and does not support claiming that reverse crunches directly burn belly fat for everyone.
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I’m Julie Lohre, an IFBB Fitness Pro and certified personal trainer and nutrition specialist. For more than 20 years I have helped women over 40 get stronger, leaner, and more confident through personalized online coaching built around their real lives.